ext4: add inline encryption support

Wire up ext4 to support inline encryption via the helper functions which
fs/crypto/ now provides.  This includes:

- Adding a mount option 'inlinecrypt' which enables inline encryption
  on encrypted files where it can be used.

- Setting the bio_crypt_ctx on bios that will be submitted to an
  inline-encrypted file.

  Note: submit_bh_wbc() in fs/buffer.c also needed to be patched for
  this part, since ext4 sometimes uses ll_rw_block() on file data.

- Not adding logically discontiguous data to bios that will be submitted
  to an inline-encrypted file.

- Not doing filesystem-layer crypto on inline-encrypted files.

Co-developed-by: Satya Tangirala <satyat@google.com>
Signed-off-by: Satya Tangirala <satyat@google.com>
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Link: https://lore.kernel.org/r/20200702015607.1215430-5-satyat@google.com
Signed-off-by: Eric Biggers <ebiggers@google.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index 64fe82ec65ff..dc5e05b47646 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -320,9 +320,8 @@ static void decrypt_bh(struct work_struct *work)
 static void end_buffer_async_read_io(struct buffer_head *bh, int uptodate)
 {
 	/* Decrypt if needed */
-	if (uptodate && IS_ENABLED(CONFIG_FS_ENCRYPTION) &&
-	    IS_ENCRYPTED(bh->b_page->mapping->host) &&
-	    S_ISREG(bh->b_page->mapping->host->i_mode)) {
+	if (uptodate &&
+	    fscrypt_inode_uses_fs_layer_crypto(bh->b_page->mapping->host)) {
 		struct decrypt_bh_ctx *ctx = kmalloc(sizeof(*ctx), GFP_ATOMIC);
 
 		if (ctx) {
@@ -3046,6 +3045,8 @@ static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
 	 */
 	bio = bio_alloc(GFP_NOIO, 1);
 
+	fscrypt_set_bio_crypt_ctx_bh(bio, bh, GFP_NOIO);
+
 	bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
 	bio_set_dev(bio, bh->b_bdev);
 	bio->bi_write_hint = write_hint;